The present invention relates to a clear and stable, highly alkaline composition with controlled foaming, containing a high amount of surface active nonionic alkylene oxide adduct and a hexyl glycoside as a hydrotrope. This composition has a very good wetting and cleaning ability and can be used for cleaning of hard surfaces, in a mercerization process and for a cleaning, desizing or scouring process of fibres and fabrics.
Highly alkaline compositions, such as concentrates having a high content of alkaline agents, such as alkali hydroxides, alkaline complexing agents and silicates, and having a pH value above 11, preferably above 13, are frequently used for cleaning of hard surfaces, for mercerization, scouring etc. A good wetting ability combined with a good cleaning effect is essential in the above-mentioned applications, which requires the presence of considerable amounts of suitable surfactants to lower the high surface tension caused by the high amount of electrolytes. It is also important to have a controlled foaming in these systems. To minimize the cost of transportation, these concentrates should contain as small amounts of water and other solvents as possible. It is also advantageous if the concentrates remain homogenous during transportation and storage.
Since these compositions contain high amounts of electrolytes, such as alkali and/or alkaline complexing agents, it is difficult to dissolve larger amounts of surfactants, especially nonionic surfactants. Therefore, in order to improve the solubility, hydrotropes are often added, and the most commonly used hydrotropes are ethanol and sodium xylene or cumene sulphonate. Ethanol is rather efficient, but presents an explosion hazard, and sodium xylene or cumene sulphonate is relatively inefficient at higher surfactant levels. If a surfactant that is soluble in alkaline water solutions without the addition of a hydrotrope is used, there will be a problem with too much foam, which requires the addition of a foam depressor.
Alkyl glycosides have earlier been used in highly alkaline compositions, see for example EP-B1-589 978, EP-A1-638 685 and U.S. Pat. No. 40,240,921. Furthermore, alkyl glycosides are well known as active cleaning agents in commonly used cleaning compositions, see e.g. WO 97/34971, U.S. Pat. No. 4,627,931 and EP-B1-075 995.
EP-B1-589 978 describes the use of C8-C14 alkyl glycosides as surface active auxiliaries in the desizing, bleaching and alkaline scouring of natural and/or synthetic sheet-form textile materials, yarns or flocks, while EP-A1-638 685 relates to a mercerizing wetting agent containing, either alone or in combination, a C4-C18 alkyl glycoside, a C4-C18 alkyl glyconic amide and the corresponding sulphonated derivatives. Liquid highly alkaline cleaning concentrates containing an alkyl glycoside or an alkyl glycidyl ether and surface active nonionic alkylene oxide adducts are described in U.S. Pat. No. 4,240,921. The preferred alkylene oxide adducts are the ones capable of acting as foam depressors, such as polyoxyethylene/polyoxypropylene block copolymers and capped alcohol ethoxylates. The concentrate contains
a) 10 -35% by weight of alkali metal hydroxide,
b) 10 -50% by weight of a mixture of a first nonionic surfactant which is a polyoxypropylene polyoxyethylene condensate that acts as a foam depressor and a second nonionic surfactant which is a capped ethoxylated alcohol together with an alkyl glycoside or an alkyl glycidyl ether, where the weight ratio between the alkyl glycoside or the alkyl glycidyl ether and the before-mentioned first and second nonionic surfactants is between 5:1 to 10:1 and
c) water to balance.
These concentrates are used to formulate low foaming cleaning compositions having utility e.g. in the food industry.
However, the above composition disclosed in U.S. Pat. No. 4,240,921 requires a rather high ratio of alkyl glycoside to the other nonionic surfactants present in the composition. Further, it is well known that the inclusion of larger amounts of PO in an alkoxylate, such as in foam depressors of the Pluronic type, has a negative influence on the biodegradability of the product. Finally, a capped alcohol ethoxylate normally is a poor wetting agent and has in addition a low cleaning ability. Its presence also increases the need for an extra amount of the alkyl glycoside or alkyl glycidyl ether.
There is consequently a need for highly alkaline compositions with improved properties.
The present invention generally relates to a method for improving the solubility of a surface active nonionic alkylene oxide adduct in a highly alkaline composition, said adduct containing a hydrocarbon group or an acyl group of from 8 to 24 carbon atoms and at least one primary hydroxyl group in the alkoxylated part of the molecule, said method comprising adding a hydrotrope to said highly alkaline composition, said hydrotrope comprising a hexyl glycoside having the formula
C6H13OGnxe2x80x83xe2x80x83(I),
where G is a monosaccharide residue and n is from 1 to 5.
The invention also relates to a composition having a pH value above 11, which contains
a) 3-50% by weight of alkali hydroxide and/or alkaline complexing agents,
b) 0.05-30% by weight of a surface active nonionic alkylene oxide adduct having a hydrocarbon group or an acyl group of from 8 to 24 carbon atoms and having at least one primary hydroxyl group in the alkoxylated part of the molecule,
c) 0.04-30% by weight of a hexyl glycoside, and
d) 20-97% by weight of water.
It has now been found that highly alkaline compositions having a pH above 11, preferably at least 13 and most preferably above 13.7, that exhibit an excellent cleaning and wetting ability, can be prepared by using a hexyl glycoside having the formula
C6H13OGnxe2x80x83xe2x80x83(I),
where G is a monosaccharide residue and n is from 1 to 5, as a hydrotrope for a surface active nonionic alkylene oxide adduct that is not soluble in the highly alkaline composition and contains a hydrocarbon group or an acyl group of from 8 to 24 carbon atoms and at least one primary hydroxyl group in the alkoxylated part of the molecule. Suitably the adduct has the formula
R(AO)x(C2H4O)yHxe2x80x83xe2x80x83(II),
where R is an alkoxy group Rxe2x80x2Oxe2x80x94 having 8 to 24 carbon atoms or a group Rxe2x80x3CONRxe2x80x2xe2x80x3xe2x80x94, where Rxe2x80x3 is a hydrocarbon group having 7 to 23 carbon atoms, Rxe2x80x2xe2x80x3 is hydrogen or the group xe2x80x94(AO)x(C2H4O)yH, preferably hydrogen, AO is an alkyleneoxy group with 2-4 carbon atoms, x is a number from 0 to 5 and y is a number from 1 to 10.
The present invention also relates to a composition having a pH value above 11, which contains
a) 3-50% by weight of alkali hydroxide and/or alkaline complexing agents,
b) 0.05-30% by weight of a surface active nonionic alkylene oxide adduct having a hydrocarbon group or an acyl group of from 8 to 24 carbon atoms and having at least one primary hydroxyl group in the alkoxylated part of the molecule,
c) 0.04-30% by weight of a hexyl glycoside, and
d) 20-97% by weight of water.
The weight ratio between the hexyl glucoside and the nonionic surfactant according to formula II is from 1:10 to 10:1, preferably from 1:10 to 4:1.
It should be pointed out that alkyl glucosides have been used in less alkaline detergent compositions, where the conditions are different. Examples of such compositions are to be found in U.S. Pat. No. 4,488,981 and EP-B1-136 844.
U.S. Pat. No. 4,488,981 and EP-B1-136 844 describe the use of C2-C6 alkyl glycosides for reducing the viscosity of and preventing phase separation in an aqueous liquid detergent, for instance in liquid shampoos and soaps and in heavy duty liquids. The C2-C4 alkyl glycosides are the most preferred alkyl glycosides, since they are most effective in reducing the viscosity.
Furthermore, in U.S. Pat. No. 5,525,256 and in Statuary Invention H 468 industrial and institutional alkaline liquid cleaning compositions containing C8-C25 alkyl glycosides as cleaning agents are described.
However, none of these references discloses the unexpected effects of hexyl glycosides in highly alkaline cleaning compositions, containing at least 3%, preferably at least 20% alkali and/or alkaline builders and having a pH-value above 11, preferably at least 13, and most preferably above 13.7.
Suitable examples of nonionic surfactants according to formula II are alkylene oxide adducts obtained by alkoxylation of an alcohol or an amide. The R group in formula II may be branched or straight, saturated or unsaturated, aromatic or aliphatic. Examples of suitable hydrocarbon groups Rxe2x80x2 are 2-ethylhexyl, octyl, decyl, cocoalkyl, lauryl, oleyl, rape seed alkyl and tallow alkyl. Especially suitable hydrocarbon groups Rxe2x80x2 are those obtained from oxoalcohols, Guerbet alcohols, methyl substituted alcohols with 2-4 groups having the formula xe2x80x94CH(CH3)xe2x80x94 included in the alkyl chain, and straight alcohols. Other suitable R groups are the Rxe2x80x3CONHxe2x80x94 aliphatic amido groups, where Rxe2x80x3CO is preferably derived from aliphatic acids such as 2-ethylhexanoic acid, octanoic acid, decanoic acid, lauric acid, coconut fatty acid, oleic acid, rape seed oil fatty acid and tallow fatty acid.
The alkali hydroxide in the composition is preferably sodium or potassium hydroxide. The alkaline complexing agent can be inorganic as well as organic. Typical examples of inorganic complexing agents used in the alkaline composition are alkali salts of silicates and phosphates, such as sodium tripolyphosphate, sodium orthophosphate, sodium pyrophosphate, sodium phosphate and the corresponding potassium salts. Typical examples of organic complexing agents are alkaline aminopolyphosphonates, organic phosphates, polycarboxylates, such as citrates; aminocarboxylates, such as sodium nitrilotriacetate (Na3NTA), sodium ethylenediaminetetraacetate, sodium diethylenetriaminepentaacetate, sodium 1,3-propylenediaminetetraacetate and sodium hydroxyethylethylenediaminetri-acetate.
The wetting of the composition is attributable to the nonionic surfactant present. The hexyl glycoside is not a wetting agent in itself, but by acting as a hydrotrope for the surfactant it enhances the wetting ability of the composition, since the otherwise insoluble surfactant now is dissolved and can exert its wetting ability. Concentrates with unexpectedly high amounts of surfactants can be dissolved in a highly alkaline aqueous phase, and the amount of hydrotrope needed to obtain a stable, clear concentrate or composition is less than in prior art. This is very surprising, since in formulations with other short-chain alkyl glycosides, it is not possible to include as large amounts of surface active nonionic alkylene oxide adducts as when n-hexyl glucoside is present in the formulations. For a comparison, formulations have also been made with both shorter and longer alkyl glucosides, which is illustrated in Example 1.
The composition of the present invention also exhibits a controlled foaming without the need to add foam depressors as those used in prior art. The products in the composition all have good environmental properties. They are readily biodegradable and of low toxicity.
The composition has an excellent wetting and cleaning ability and can advantageously be used for the alkaline cleaning of hard surfaces, e.g. vehicle cleaning, in a mercerisation process and for a cleaning, desizing or scouring process of fibres and fabrics performed at a pH above 11.
When used for the cleaning of hard surfaces, the composition is normally diluted with water prior to use, whereas in a mercerisation process, the composition can be used as such. For the cleaning, desizing and scouring of fibres and fabrics the composition could either be used as such or diluted.
When producing woven fabrics, the warp threads are subject to extreme stresses and must therefore be provided with a protective coatingxe2x80x94the sizing agentxe2x80x94that adheres to the fibre, forming an abrasion-resistant, elastic film. The two main groups of sizing agents are macromolecular natural products and their derivatives, e.g. starches and carboxymethyl cellulose, and synthetic polymers, e.g. polyvinyl compounds. The sizing agent must be completely removed when the cloth has been woven, since it usually has a deleterious effect on subsequent finishing processes. The desizing process can be enzymatic or oxidative and is usually carried out to completion in the subsequent alkaline scouring and bleaching stages, where the initially water-insoluble starch degradation products and the residual sizes are broken down partly hydrolytically and partly oxidatively and removed.
During the scouring, intra- and intermolecular hydrogen bonds of cellulose are broken, and the polar hydroxyl groups of the polysaccharide are solvated. Transport of impurities from the inside to the outside of the fibre occurs. In the alkaline environment hydrolytic decomposition of different plant parts takes place and fats and waxes are also hydrolysed. The alkali concentration used is ca 4-6% when using NaOH.
In the scouring process there is a need for auxiliaries to effect thorough wetting, emulsification and dispersion of water insoluble impurities, complexation of heavy metal ions and prevention of.fibre damage by atmospheric oxygen. Here alkali-stable wetting agents and detergents constitute an important group of additives. It is also very important that an adequate amount of wetting agent/detergent is dissoluble in the alkaline water solution, which often requires the addition of a hydrotrope. The same applies to an even greater extent for the mercerization process, which is performed principally in order to improve the dyeability of cotton. The process involves treatment of cotton under tension with a ca 20-26% caustic soda solution at 15-25xc2x0 C. for 25-40 s. This treatment destroys the spiral form of cellulose, whereby the accessibility to water and, consequently, to water-based dyes, is improved. In addition to a good wetting ability and alkaline stability, it is also important that the additives do not cause foaming, since this would impede the rapid wetting required in the mercerization baths.